ax_gcc_archflag

Synopsis

AX_GCC_ARCHFLAG([PORTABLE?], [ACTION-SUCCESS], [ACTION-FAILURE])

Description

This macro tries to guess the "native" arch corresponding to the target
architecture for use with gcc’s -march=arch or -mtune=arch flags. If
found, the cache variable $ax_cv_gcc_archflag is set to this flag and
ACTION-SUCCESS is executed; otherwise $ax_cv_gcc_archflag is set to
"unknown" and ACTION-FAILURE is executed. The default ACTION-SUCCESS is to
add $ax_cv_gcc_archflag to the end of $CFLAGS.

PORTABLE? should be either [yes] (default) or [no]. In the former case, the
flag is set to -mtune (or equivalent) so that the architecture is only used
for tuning, but the instruction set used is still portable. In the latter
case, the flag is set to -march (or equivalent) so that
architecture-specific instructions are enabled.

The user can specify –with-gcc-arch=<arch> in order to override
the macro’s choice of architecture, or –without-gcc-arch to
disable this.

When cross-compiling, or if $CC is not gcc, then ACTION-FAILURE is called
unless the user specified –with-gcc-arch manually.

Requires macros: AX_CHECK_COMPILE_FLAG, AX_GCC_X86_CPUID

(The main emphasis here is on recent CPUs, on the principle that doing
high-performance computing on old hardware is uncommon.)

License

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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.

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